Introduction
In 1939 the British parliament removed covenants protecting old grasslands from ploughing restrictions (Duffey et al., 1974).This, coupled with a desire for self-sufficiency, accentuated by the onset of the Second World War, marked the start of intensive agriculture in the United Kingdom. This intensification substantially increased between the 1940s, when two thirds of Britain’s food was imported (Lloyd and Wibberley, 1977), and the 1980s when overproduction and subsequent detrimental effects on the environment were causing concern. By 1984 production of cereals was 10 million tonnes more than the population of the UK could utilize (Marren, 2002). Increased mechanisation and inorganic fertiliser use, as well as new strains of pasture species, including ryegrass and clover, created highly productive but species-poor swards.